The present invention relates to a medical waste disposal apparatus for the safe and efficient disposal of contagious medical waste including used plastic syringes and injection needles.
The number of different kinds of waste is increasing with the diversification of industry. Some types of waste can be relatively easily disposed of by simple burning or heating, while others, such as infectious medical waste, cannot. As infectious medical waste is burned or heated, an environmentally or hygienically harmful gaseous pyrolytic product is generated. Contagious medical waste may include used plastic syringes, injection needles, or surgical operation gloves. Since these types of medical waste are typically infectious, they cannot simply be thrown away. For that reason, the waste is recovered in a prescribed container, and later placed in a bag or the like. The waste may be shredded by a shredder, if necessary, before being placed in the bag or the like. The waste can subsequently be disposed of by burning in an incinerator, sterilization by high-pressure steam, or heating. The combustion gases resulting from burning the waste can be partially removed by an appropriate dust collector. However, there are disadvantages in that the soot of the burned waste cannot be completely eliminated. Furthermore, it is necessary to employ large equipment, which is expensive to purchase, operate, and maintain. When the waste is sterilized, it may, for example, be heated to a temperature of 126.degree. C. to 131.degree. C. Since these temperatures are relatively low, the waste is only slightly pyrolyzed, and it is not necessary to provide means for disposing of a gas, smell or the like resulting from the sterilization. However, since the temperature is relatively low, some waste will not be sterilized. To heat the waste, an apparatus including an appropriate melting container, in which the waste is heated at a temperature of approximately 200.degree. C. by a heating furnace, is provided. One example of such waste containers for processing is disclosed in Japanese Patent Application 281756/90. These apparatus typically exhibit good sterilization characteristics, have a simple structure, are not too large and are easy to maintain and operate. Furthermore, since heating furnaces, such as electric furnaces, are hermetically closed throughout the heating process, a pyrolytic product will not be expelled into the surrounding air. Therefore, the heating of medical waste is a very effective procedure from an environmental standpoint.
If a hospital syringe or the like, made mainly of polypropylene, is heated at a temperature of 200.degree. C. for sterilization by the above-mentioned heating apparatus, a large quantity of pyrolytic products such as tar, acetic acid and acetaldehyde are generated from the heated material, usually at a temperature of between 170.degree. C. and 180.degree. C. The processed waste is ordinarily not removed from the incinerator until the incinerator has cooled adequately. Nonetheless, if tar and a gaseous pyrolytic product, such as acetaldehyde, acetic acid or acetone, are generated during the heating process and remain in the incinerator thereafter, the gaseous pyrolytic product may escape from the incinerator when the waste is removed. Furthermore, if the plastic syringe, having a melting point around 170.degree. C., and an instrument made of polyvinyl chloride, having a much lower melting point than the syringe, are melted simultaneously by the apparatus or the incinerator described above, a harmful gas including hydrogen chloride may be generated, a gas which will likely escape from the apparatus or the incinerator at the time of removal of the processed waste. Furthermore, used syringes and the like typically contain a lot of moisture due to remaining blood or other liquid contents. The moisture becomes steam in the heating apparatus or the incinerator and fills the interior thereof during processing. The generated steam is likely to adhere to the cooled parts of the apparatus or the incinerator, at the time of cooling, after processing, and will cohere as water drops which remain in the apparatus or the incinerator for long periods of time, potentially resulting in short circuiting of the electric wirings of the incinerator.